Ecological and biological studies on olive psyllid, Euphyllura straminea loginove and its control on olive trees in Egypt

Olive psyllid, Fuphyllura ,straminea I.oginova (Homoptera: Psylloidea: Aphalaridae) become a key pest during the last few years on olive trees in the main centers of olive groves in Egypt. This species seemed to be a monophagou species. E.cological and population studies on this species at three different ecosystems were carried out throughout two successive years. Obtained results revealed that population of this species was more abundant at desert ecosystem than agricultural ecosystem, while it was less abundant at coastal ecosystem. Insect population found to be active at the three ecosystems during winter and spring seasons, while it was less active during summer and autumn seasons. This species was aestivated on buds of terminal twigs, suckers and water shoots of olive trees during this period. The seasonal abundance of different developmental stages of this species reached its maximum peak during April at the three localities. During this period the olive trees were at sprouting of vegetative and floral buds. Therefore, the activity of this species was coinciding with the phenology of olive trees. Also, result revealed that this species passed through one annual generation. The adult females were dominant than adult males and sex ratio was about 4:1 under field conditions. The main weather factors (means maximum, minimum temperatures and mean percentages of relative humidity) either each single factor or as group showed negative significant effects on the changes in population density throughout the year. Therefore, the thermal requirements of this species seemed to be relatively low and temperature zone of activity ranging between 18-27ºC. Biological studies on olive seedlings at three constant temperatures (20, 25 andºC ) throughout one complete generation were carried out. Results revealed that 25°C found to be the optimum condition for rearing this species. At this degree the highest percentages of egg hatchability, adults emergence and female fecundity reached their maximum values, also percentages of mortalities of different developmental stages reached their minimum values. 7,ero of development, rate of development and thermal constant units were calculated for all developmental stages. Also, life- table parameters showed that 25°C was optimum degree, where female fecundity and net reproductive rate, intrinsic rate of increase and finite rate of increase recorded their maximum values, while population doubling time recorded its minimum values. Results of evaluation of damages caused by this species revealed that population density had positive relationship with percentage of dropping flowers, while population density had negative relationships with percentages of fertile flower, fruit set and olive fruit yield. Results of estimation of economic levels of infestation showed that when population density less than 4 nymphs / twig could be regards as General Fquilibrium Position, when population ranged between 4.0- 4.5 nymphs / twig could be regards as F.conomic Threshold level, when population density ranged between 17-17.3 nymphs / twig this level could be regard as E.conomic Injury I,evel, when population density increased as ranged between 17.5-19 nymphs / twig could be regards as Economic Damage Level. Chemical control experiments were carried out under insectary , conditions to evaluate the toxic and repellent effects of natural products (3,4 dihydroxyphenolethanol). Results showed that this compound had toxic and repellent effect on both nymphs and adults. Its efficiency was increased as concentrations increased. Therefore, this compound could be used on olive trees during blooming period to protect them from infestation with this species. Field experiments were carried out to evaluate the efficiency of six insecticides as spray just before blooming. Results revealed that two phosphorus compounds, Sumithion at 0.3% gave 98.6% reduction in population and Imidan at 0.1 % gave 98.1 % reduction in population while, mineral oil Super Royal at 1.5% gave 95.3% reduction in population.